Exhaust systems for smaller and medium-sized watercraft generally include, in the direction of flow of the exhaust gases downstream from the engine or engines, one or more compensators for damping the vibrations, silencers and an exhaust pipe that leads to an outlet in the side of the watercraft. Said outlet is typically located just above the waterline, in order to keep the discharged exhaust gases as far away as possible from the deck of the watercraft and from the decks of neighboring watercraft.
Due to the high temperature of the exhaust gases, it is necessary that they be cooled before passing through the side of the vessel. This is usually done by injecting seawater directly into the exhaust pipe, said water then being swirled with the flow of exhaust gases and ejected with the latter through the exhaust pipe.
This way of cooling the exhaust gases is very efficient. One problem with it, however, is that, due to direct contact between the seawater and the exhaust gases, and the relatively long duration of this contact throughout the entire transport path to the outlet, uncombusted fuel and soot particles are deposited in the cooling water and flushed out from the exhaust pipe along with the water. As a consequence, a film of soot and fuel particles is formed on the water surface around the outlet, on the side of the vessel and on neighboring watercraft.
Another consequence of seawater being injected directly into the exhaust pipe is that the exhaust pipe is clearly susceptible to corrosion in the area around the seawater injection duct.
Another problem with unpleasant consequences for the exhaust system is the beating of waves; when heavy seas or swell leads to water masses beating against the side of the vessel in the area of the outlet opening, thus penetrating into the exhaust system, this can lead to substantial damage. In order to avoid such damage as far as possible, a known method is to have the exhaust pipe describe a U-shape shortly before the outlet, and to have the vertex of the U positioned as high as possible above the water surface. However, it has become evident that, under unfavorable conditions, this precautionary arrangement is not sufficient, either, for seawater that has been washed into the system to be stopped before reaching the vertex of the U. If seawater does penetrate beyond said vertex, considerable damage to the compensators, the silencer or to the engine as a result of corrosion is pre-programmed.
The object of the invention is, therefore, to provide an exhaust system for watercraft in which corrosion damage from seawater is largely prevented.
In accordance with the invention, that object is attained with an exhaust system for watercraft that has an exhaust pipe leading from an engine system to an exhaust gas outlet, wherein a through-flow means for degrading the energy of seawater gushing through the exhaust gas outlet into said exhaust pipe is provided in the section of said exhaust pipe preceding the exhaust gas outlet, and that at least one settling basin is provided in the area of said means for degrading the energy of seawater, or upstream thereof in the direction of exhaust gas flow, and a drainage conduit leads from the deepest point of the settling basin into the surroundings of the vessel.
An advantageous embodiment is one in which the settling basin is disposed higher than the exhaust gas outlet.
A further advantageous embodiment is one in which the means for energy degradation is defined by at least one elbow in, and the settling basin by a section of the exhaust pipe that is located between a downward section and a subsequent upward section of said exhaust pipe.
In the latter case, the elbow in the pipe is preferably defined by two 180xc2x0 bends that curve in the same direction along a helix and hence can be installed in a space-saving manner. It is then advantageous when the first bend closest to the exhaust gas outlet when viewed contrary to the direction of exhaust gas flow is comprised of a first upward branch and a second downward branch, and that the second bend following thereafter defines the settling basin and commences with a first downward branch and ends with a second upward branch.
In an exhaust system in which the exhaust gases are cooled with seawater, the place where cooling seawater is fed into the exhaust gas is preferably located downstream from the first bend. This proves to be particularly advantageous when the end member at the outlet end of the exhaust pipe is at least partially enclosed in a cooling-water jacket.